1. Field of the Invention
The present invention is directed to a method and to a system for the imposition of print data, particularly for processing a digital print data stream.
2. Description of the Related Art
A special area, what is referred to as “Print on Demand” (PoD) has arisen in the field of digital printing. A corresponding POD system has been described, for example, under the title “Entwicklung neuer Medien-Konzepte für POD-Dienstleister” in the periodical Deutscher Drucker, No. 35/98 of 17 Sep. 1998.
Compared to conventional offset book printing, the advantages of such POD systems are that printed matter can be produced in a short time (just-in-time). Small editions of about 2 through 2000 copies can thus be economically published. A specific, currently required number of books can thus be printed in a short time on demand. Costs for warehousing as well as for remainders of books can thus be eliminated.
On the other hand, there is the necessity in POD systems of likewise designing the layout of the printout in high-performance fashion, particularly the imposition of the print data. Whereas a relatively great deal of time is available for these procedures in conventional book printing, this procedure must be accomplished in a relatively short time in POD systems in order to be able to achieve the aforementioned advantages of a just-in-time production. This requirement is countered, on the one hand, by the fact that there are numerous setting possibilities and demands during the course of a print production of books or bound brochures. In a POD printing system, a post-processing system following the printer device is usually connected, this compiling the material printed by the printing system to form a printed document such as a book or a brochure. For example, a saddle binder or a spiral binder can be provided following the printer device so that the printed pages are bound therewith to form a book or a brochure.
Further, a folding device can be provided between the printer device that prints the recording medium and the binding system when the POD printing system generates printed matter in signatures. The fundamentals and various specific brochure “Folding Techniques” issued by Stahl GmbH, a subsidiary of Heidelberger Druckmaschinen AG, 69115 Heidelberg, Order No. 1-800-437-7388 (Heidelberger). The content of this document is herewith incorporated by reference into the present specification. Various signature strategies and imposition patterns connected therewith are described in this document for sheet-fed printing systems and web-fed printing systems.
As already mentioned above, there is the demand in POD systems to implement the print data and, thus, the imposition event as well as in as high-performance a manner as possible, i.e. fast and largely automated. Accordingly, there is also the demand to design imposition patterns, i.e. the arrangement of the page sequence on the recording medium or, respectively, signature in as fully automated a manner as possible such that both the page sequence as well as the position of the print image on the pages of the ultimately produced printed matter (book, brochure or the like) exactly corresponds to the reading sequence. A further demand is to thereby achieve a specific registration precision of successive pages in the printed matter. This demand is opposed by the shift of the print image in signature printing caused by folding the signature and cutting the edges.
U.S. Pat. No. 4,672,462 discloses a method and a system for recording a plurality of images on a light-sensitive film, whereby the images correspond to several pages of conventional book bindings. The layout of the print images is adapted to the binding before the exposure in conformity with the prescriptions of an operator.
European Patent reference EP-A-741 877 B1 or, respectively, International Published Application WO-A-95/20185 corresponding thereto discloses a printing system wherein various post-processing systems for processing the page stream printed on the paper through a device for binding documents are connected to a printer device.
European Patent reference EP-A-0 608 685 discloses a device for producing brochures from images that have been read in. For generating printed pages according to prescriptions, the images are automatically turned and adapted in terms of their dimensions.
U.S. Pat. No. 5,398,289 discloses a method and a system for printing signatures. Upon output of individual sheets having up to four print pages, a position of the print images in the printing that is not exactly registered is corrected, this position having arisen as a result of a folding of the signature at the back margin. However, U.S. Pat. No. 5,398,289 discloses no possibility for correcting the print image shift on sheets caused by folding, said sheets having a plurality of fold axes for producing signatures.